Short-term kitempowerDX
Standard Radon Test short-term mail-in radon test kit
- Lab fee included
Method: Passive sampler
In home: 48 to 96 hours
Locations and reports
Radon Levels in Mono County, California
EPA puts Mono County in Zone 2, its middle radon zone, and only 20 radon tests from it are on file with CDC (2008 to 2017, laboratory totals). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Highest bordering
37.0%
Douglas County
- Douglas
- 37.0%
- Fresno
- 11.0%
5 of 9 neighbours have 30+ tests, 2008 to 2017
Nearest county
23.0%
Tuolumne County, 59 miles
- Tuolumne
- 23.0%
- California
- 10.3%
Share at 4+ pCi/L, 74 tests, 2008 to 2017
Ground above low
100.0%
57.3 pts above California
- Mono
- 100.0%
- California
- 42.7%
Share of land USGS rates moderate or high potential
Tests reported
20
Too few for a share
- Mono
- 20
- Needed
- 30
2008 to 2017, laboratory
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
EPA predicts 2 to 4 pCi/L indoors
Read a result for Mono County
Starts at EPA's action level
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.0 pCi/L
At or above 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher.
The data
Mono County, At a glance
Mono County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Mono County is a
USGS geologic potential: Moderate across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Mono County, 2008 to 2017, laboratory
CDC holds 20 reported tests for Mono County over the 2008 to 2017 laboratory totals, with a median of 4.6 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Mono County beside the counties around it is how this page reads it.
What these figures count
Only 20 tests were reported to CDC for Mono County over 2008 to 2017 (laboratory totals), and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.
Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).
Mono County, Compared
Mono County radon figures, compared
Calculated by Radon411CDC's largest figure for Mono County rests on 20 tests over the 2008 to 2017 laboratory totals, 10 of them at or above 4 pCi/L, so each test moves its share by 5.0 points and no rank or comparison is drawn from it. Results reached as high as 27.0 pCi/L, with a middle value of 4.6 pCi/L.
Of the counties bordering it, 5 have a figure over the 2008 to 2017 laboratory totals: Douglas County, NV reported the largest share at or above 4 pCi/L, 37.0%, and Fresno County the smallest, 11.0%, with Lyon County, NV at 30.4%, Tuolumne County at 23.0% and Madera County at 14.7% between. Farther out, Calaveras County (93 miles away) at 17.6%, Amador County (102 miles away) at 27.8% and El Dorado County (106 miles away) at 30.3% have figures too. Pooled across 56 California counties, 10.3% of reported tests reached that level; across every county in the country with a figure, 35.7%.
Statewide for the same period, El Dorado County reported the highest share (30.3%) and Sonoma County the lowest (0.8%). EPA's 1993 map puts Mono County in Zone 2, its middle label: a predicted county average between 2 and 4 pCi/L. USGS geology rates 100% of the county's land moderate radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Mono County, Geology
The ground under Mono County
PredictedUSGS's geologic map puts all of Mono County's mapped land in one class: moderate radon potential. The map puts 84.9% of Mono County in the area it calls Basin and Range and 15.0% in Sierra Nevada. USGS gives both a radon index of 9, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Basin and Range | Precambrian metamorphic rocks, late Precambrian and Paleozoic metamorphosed and unmetamorphosed sedimentary rocks, Mesozoic and Tertiary intrusive rocks, and Tertiary sedimentary and volcanic rocks. | Moderate | 9 | 84.9% |
| Sierra Nevada | Northern Sierra Nevada is underlain primarily by Paleozoic and Mesozoic metamorphic rocks. Granitic rocks predominate in the southern Sierrra Nevada , with lesser Mesozoic metamorphic rocks. | Moderate | 9 | 15.0% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Mono County beside the ground around it
Across California 0.1% of the land is rated high; none of Mono County's is. Of the 9 counties that border it, 4 have more high-potential ground, Mineral County, NV the most at 13.6%.
The map rates the ground, not the air in any home.
Local help
Mono County, Local resources
Radon testing and mitigation in Mono County
- California Indoor Radon ProgramCalifornia Indoor Radon Program, run by California Department of Public Health, licenses or certifies radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in California.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Discounted test kits can be purchased through our partner laboratory, Alpha Energy, for $14.95.
- Compare kits
- Professionals in California4 professionals are listed in California.
What California's program says
- Phone
- 1-800-745-7236
- Radonprogram@cdph.ca.gov
- Licensing of radon professionals
The Radon Program certifies all radon service providers operating in California.
What it means
Mono County, Questions
Questions about radon in Mono County
Are radon levels high in Mono County?
Over the 2008 to 2017 laboratory totals, 50.0% of the radon tests reported to CDC for Mono County, California were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.6 pCi/L. Of the counties bordering it, 5 have a figure over the 2008 to 2017 laboratory totals: Douglas County, NV reported the largest share at or above 4 pCi/L, 37.0%, and Fresno County the smallest, 11.0%, with Lyon County, NV at 30.4%, Tuolumne County at 23.0% and Madera County at 14.7% between.
Which counties border Mono County?
Mono County borders 9 counties: Tuolumne County, CA, Mineral County, NV, Alpine County, CA, Douglas County, NV, Lyon County, NV, Madera County, CA, Esmeralda County, NV, Fresno County, CA and Inyo County, CA.
Products
Mono County, Products
Testing a home in Mono County
No CDC figure names Mono County; the nearest county with one, Tuolumne County (59 miles away), reported 23.0% of its tests at or above 4 pCi/L over the 2008 to 2017 laboratory totals, the only reading nearby until a test of this home. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Mono County; a long-term test tells the year-round average.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
Monitor
Corentium Home 2 battery digital radon monitor
- C-NRPP 2024/25: Not included
- Battery
- Bluetooth
- Screen, app
Method: Alpha spectrometry
Readings: Every 60 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Mono County, Bordering counties
Counties bordering Mono County
Calculated by Radon411- Radon levels in Alpine County, CAEPA zone 2
63.2%at or above 4 pCi/L
Median 4.5 pCi/L · 19 tests
- Radon levels in Inyo County, CAEPA zone 2
50.0%at or above 4 pCi/L
Median 4.0 pCi/L · 14 tests
- Radon levels in Douglas County, NVEPA zone 1
37.0%at or above 4 pCi/L
Median 3.1 pCi/L · 1,617 tests
- Radon levels in Mineral County, NVEPA zone 1
33.3%at or above 4 pCi/L
Median 3.5 pCi/L · 6 tests
- Radon levels in Lyon County, NVEPA zone 1
30.4%at or above 4 pCi/L
Median 2.6 pCi/L · 303 tests
- Radon levels in Tuolumne County, CAEPA zone 2
23.0%at or above 4 pCi/L
Median 1.4 pCi/L · 74 tests
- Radon levels in Madera County, CAEPA zone 2
14.7%at or above 4 pCi/L
Median 1.4 pCi/L · 34 tests
- Radon levels in Fresno County, CAEPA zone 2
11.0%at or above 4 pCi/L
Median 1.5 pCi/L · 100 tests
- Radon levels in Esmeralda County, NVEPA zone 2
No CDC figure for 2008 to 2017; its page reads it against its own neighbours.
Mono County, Cities and towns
Cities and towns in Mono County
Mono County has been losing residents: from 13,222 in 2020 to 12,505 on July 1, 2025, a fall of 5.4% by the Census Bureau's estimates. Spread over its land, that is 4.1 people to the square mile. Mammoth Lakes, its one incorporated place, has 6,867 residents, 54.9% of the total. Testing is reported here more often than across the state: CDC's 20 reported tests for 2008 to 2017 come to 1.6 for every 1,000 residents (2025 estimate), against 0.2 for California.
Mammoth Lakes is the one incorporated place here; CDC publishes no figure by town, so it reads Mono County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Mammoth Lakes | 6,867 | −5.1% | 54.9% |
One incorporated place, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).
Mono County, Homes
Homes in Mono County
Mono County has 13,632 homes, and many share a building: 34% are in buildings of five or more, 44% are detached houses, against 57% across California. Half of its homes were built before 1980, close to California's 1976: 8% date from before 1960 and 13% from 2000 or later. 69% of occupied homes are lived in by their owner (California: 56%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Mono County | California |
|---|---|---|
| Housing units | 13,632 | 14,532,683 |
| Detached houses | 44% | 57% |
| In buildings of 5 or more | 34% | 24% |
| Mobile homes | 6% | 4% |
| Built before 1960 | 8% | 27% |
| Built since 2000 | 13% | 18% |
| Middle year built | 1980 | 1976 |
| Owner-occupied | 69% | 56% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.